The failure to roll out legislation making carbon monoxide detectors compulsory has been branded "unacceptable" five years after two teenage friends were killed by the gas.

Teenagers Neil McFerran and Aaron Davidson died from poisoning in August 2010 after a gas leak in a holiday apartment in Castlerock, Co Derry.

The 18-year-olds had been staying at the apartment with a third friend, Matthew Gaw, who survived. The three friends were found by relatives.

In 2012, in response to the Castlerock deaths, carbon monoxide alarms became a legal requirement in all new homes in Northern Ireland.

But an MLA for the area said legislation is vital to ensure all privately-owned buildings, including rental and holiday homes, are fitting with the life-saving equipment.

The SDLP's John Dallat has called on the Minister for Social Development Mervyn Storey to take action to prevent further tragedies.

Mr Dallat said: “The current Minister for Social Development has been in place for a short time only and I don’t blame him for the unacceptable delay in bringing forward this vital legislation.

"There is a clear need to make clear the responsibilities of private landlords in relation to both gas, electricity, fire safety measures and the provision of carbon monoxide safety measures.

“When Neil McFerran and Aaron Davidson lost their lives and their friend Matthew Gaw was lucky to survive, there was a clear commitment that safety in the private sector would be cleared up and stringent legislation would be put in place to ensure that requirements weren’t simply implied or unspoken but enshrined in law.

“That hasn’t happened and it is an indication of the inability of this Assembly to bring forward legislation which will protect the increasing number of people who are dependent on the private rented sector for accommodation.

“I sincerely hope that now that I have highlighted this glaring gap in our laws there will be a determined effort to ensure that never again will we have a repeat of what happened at Castlerock and indeed in other places where both gas and electricity defects have proven to be fatal."

In response to questions put to him about the roll-out of new legislation, Mr Storey said: "My department has responsibility for determining the statutory housing fitness standard which contains measures aimed at ensuring that dwellings are fit for human habitation.

"There are currently no explicit requirements in respect of the safety measures in question, fire, gas, electrical and carbon monoxide safety measures are implicit in many of the standard’s criteria.

"My officials are currently reviewing the standard and I hope to shortly publish a discussion document outlining options for change which include proposals on specific provision in relation to safety measures."

Earlier this year, an inquest was told a retired couple accidentally poisoned by gas cooker fumes would have survived if the grill door had been opened by a few millimetres.

John ‘Francie’ and Frances ‘Nan’ O’Reilly were found dead in January in the living room of the static caravan they had lived in for 30 years in Newcastle, Co Down.

Belfast Coroner’s Court heard they owned a gas cooker which had been the subject of a number of safety warnings about the serious risks of carbon monoxide build-up associated with operating the grill with the door closed.